Technical Field
The present invention relates to a method for producing an L-amino acid using a microorganism, and more specifically, to a method for producing an L-amino acid, such as L-lysine, L-threonine, L-tryptophan, etc. L-lysine, L-threonine, and L-tryptophan are used in industry as animal feed additives, health food ingredients, and for amino acid infusions.
Brief Description of the Related Art
To produce a target substance, such as an L-amino acid, etc., by fermentation using a microorganism, methods have been described which use a wild-type microorganism (wild-type strain), an auxotrophic strain derived from a wild-type strain, a metabolic regulation mutant strain as one of various types of drug-resistant mutant strains derived from a wild-type strain, a strain which has the characteristics of both the auxotrophic strain and metabolic regulation mutant strain, and so forth.
In recent years, recombinant DNA technology has been used to produce target substances by fermentation. For example, the ability of a microorganism to produce an L-amino acid has been improved by enhancing the expression of genes that encode L-amino acid biosynthesis enzymes (U.S. Pat. No. 5,168,056, U.S. Pat. No. 5,776,736), or by enhancing the influx of the carbon source to the L-amino acid biosynthesis system (U.S. Pat. No. 5,906,925).
The two-component system EvgAS has been identified in Enterobacteriaceae, such as Escherichia coli, etc. The function of the sensor kinase EvgS is unknown, but the response regulator transcription factor EvgA is known to regulate the transcription of many genes (Masuda, N. and Church, G. M., J. Bacteriol. 2002. 184(22):6225-6234. Escherichia coli gene expression responsive to levels of the response regulator EvgA.). EvgA is also known to positively regulate the transcription of the ydeO and gadE genes, which encode two transcription factors, YdeO and gadE, respectively. YdeO is also known to positively regulate the transcription of the gadE gene (Masuda, N. and Church, G. M., Mol. Microbiol. 2003. 48(3):699-712. Regulatory network of acid resistance genes in Escherichia coli.; Ma, Z., Masuda, N., and Foster, J. W., J. Bacteriol. 2004. 186(21):7378-7389. Characterization of EvgAS-YdeO-GadE branched regulatory circuit governing glutamate-dependent acid resistance in Escherichia coli.). However, the production of an amino acid using a microorganism with increased expression of the evgA, gadE, or ydeO genes has not been previously reported.